Left Brain / Right Brain:
Entering the Debate on Cerebral
Asymmetry
Paul Greenberg, 2015
Anoka Ramsey Community College
The Left vs. Right Controversy
• No, the other
controversy.
– http://cercor.oxfordjournals.org/conte
nt/11/9/868.full (Watkins et.al, 2001)
• How different are
different parts of the
brain?
Presentation Goals
• Approach the Cerebral
Asymmetry Debate
– What is a brain/cortex?
– Main issues
•
•
•
•
•
History of debate
Structural evidence
Functional evidence
How methods matter
Popular vs. Scientific usage
Selective Origins of Cerebral Asymmetry
225 Years of Inquiry
• Phrenology (less correct)
– Franz Gall & Johann. Spurzheim, 17901820
– Skull features show functional
localization (1/2 wrong)
• Functional localization (more correct)
– Brain damage shows functional
localization
– Paul Broca 1860s (speech)
– Carl Wernicke 1870s (listening)
– Supports Funct. Loc. And C. A.
Structural Asymmetry
• Premise: structural
asymmetry predicts
functional asymmetry
• Famous discoveries
– Visual System is Crossed
– Motor System is Crossed (and
Handedness)
– R. Sperry (Split Brain)
– Gray Matter Volume:
• More in Right frontal lobe
• More in Left occipital lobe
• Asymmetry exists
Functional Asymmetry / Dominance
Left
Right
Argued
Language
(speech,
grammar,
syntax)
Language
(rhythm, sound)
RH for general
emotion, or
divided emotion
Positive Emotion
Negative
Emotion,
Reading Emotion
Creativity,
Personality
Types - Popular
Myths
Narrow Focused
Attention
Global Vigilant
Awareness,
Spatial
Coordinates
Role in
Pathology, Indiv
Differences
Tools &
Machines
Metaphor,
Context, Implicit
Meaning, Living
Objects
RH Prosocial
LH Antisocial
Methods
• Neuropsychology
– Brain Damage
– Cognitive Testing
• Neurosurgery (Sperry)
– Split Brain
• Imaging,
Electrophysiology,
cellular/molecular,
neuroanatomy and more
Conclusion
• Cerebral asymmetry
well established
– Structural
– Functional
• Varying methods
and interpretations
– Relation to
psychopathology
• Popular overgeneralizations are
prevalent
– Keep Reading!
Iain McGilchrist
https://www.youtube.com/watch?v=dFs9WO2B8uI
References
•
Demaree, H. a, Everhart, D. E., Youngstrom, E. a, & Harrison, D. W. (2005). Brain lateralization of emotional
processing: historical roots and a future incorporating “dominance”. Behavioral and Cognitive Neuroscience
Reviews, 4(1), 3–20. http://doi.org/10.1177/1534582305276837
•
Fitzakerley, J. (2015, January 1). Lateralization of Cortical Function. Retrieved March 27, 2015.
http://www.d.umn.edu/~jfitzake/Lectures/DMED/SpeechLanguage/CorticalS_LAreas/Lateralization.html
•
Hecht D (2014). Cerebral lateralization of pro- and anti-social tendencies. Experimental Neurobiology , 23(1):1-27
•
Hervé, P.-Y., Zago, L., Petit, L., Mazoyer, B., & Tzourio-Mazoyer, N. (2013). Revisiting human hemispheric
specialization with neuroimaging. Trends in Cognitive Sciences, 17(2), 69–80.
http://doi.org/10.1016/j.tics.2012.12.004
•
Kolb, B., & Whishaw, I. Q. (2009). Fundamentals of human neuropsychology. New York, NY: Worth Publishers.
•
Nielsen, J. a, Zielinski, B. a, Ferguson, M. a, Lainhart, J. E., & Anderson, J. S. (2013). An evaluation of the left-brain
vs. right-brain hypothesis with resting state functional connectivity magnetic resonance imaging. PloS One, 8(8),
e71275. http://doi.org/10.1371/journal.pone.0071275
•
Van Whye, J. (1999, January 1). What did phrenologists actually do? Retrieved March 27,
2015.http://www.historyofphrenology.org.uk/overview.htm
•
Watkins, K. (2001). Structural Asymmetries in the Human Brain: A Voxel-based Statistical Analysis of 142 MRI
Scans. Cerebral Cortex, 11(9), 868-877.